Process for the recovery of high molecular weight carboxylic acids or their salts



Patented Mar. 12, 1940 [UNITED TATES PATENT OFFICE PROCESS FOR THE RECOVERY OF HIGH MOLECULAR WEIGHT CABBOXYLIC ACIDS R THEIR SALTS I Wolfgang Leithe, Ludwigshafen-on-tlie-Rliine, Germany, assignor to I. G. Farbenindustrie Aktiengesellschai't,

Germany No Drawing.

Frankfort on the Main,

Application June 1, 1938, Serial No.

211,273. In Germany June 4, 1937- 9 Claims.

substances, the acids are as a rule first saponified and the soaps freed from unsaponified or un-,

saponifiable constituents by extraction with solvents, the soap solution being then decomposed with acids if desired. -The unsaponifiable constituents are not, however, completely separated by the said method. For the industrial use of the carboxylic acids or their soaps, for example for the preparation of synthetic fats, laundry or toilet soaps, soap powders and the like, it is, however, frequently necessary for the unsaponifiable constituents to be separated to a great extent or practically completelyfrom the soaps.

I have now found that high molecular weight carboxylic acids or their salts which are contained in mixtures which also contain unsaponifiable organic substances can be freed in a man-,

her which is very simple technically from the unsaponified or unsaponifiable constituents by extracting the mixture with solvents for fats with an, addition of monohydric alcohols, ethers oresters of the same or of ketones having from 3 to 6 carbon atoms in the molecule. As initial materials for the said process there may be mentioned for example oxidation products of high molecular weight aliphatichydrocarbons; as for example of paraifin waxes, paraffin oils, middle oils, hydrogenation products of coals and tars,

oxidation products of montanwax and of mineral wax. saponification products of waxes, such as beeswax, carnauba wax, 'montan wax,

wool grease andalsosaponification products of sperm oil or train oil may also be freed from ,unsaponified or unsaponifiable constituents in the said manner.

As solvents for fat there may be mentioned for example benzine or other liquid hydrocarbons, suchas benzene, toluene or xylene, and also halogen-hydrocarbons, as for example carbon tetrachloride, trichlorethylene or chlorbenzene; carbon disulphide or ethers, such as di-isobutylether are also suitable. Suitable monohydricw alcohols, esters, ethers and ketones having from 3 to 6 carbon atoms in the molecule are for example propyl and isopropyl alcohol, the various butyl, amyl or hex-yl alcohols or mixtures of. the

same and. also acetone, methyl ethyl ketone, diethyl ethenethyl acetate and the like. The said alcohols or the like are usually employed in amounts of from about 3 to 25 per cent, advantageously of from 10 to 20 per cent, with refer-.

ence to the fat solvent. Generally speaking aqueous soap solutions containing not more than about 30 per cent of soap are used. When the soap solutions have a higher concentration, it is preferable to add thereto before treatment with the said solvents such an amount of water that i a from 20 to 30 per cent soap solution is formed.

The treatment with the solvent may be carried out at ordinary or elevated temperature depending on the nature of the saponification mixture. It is preferable to work under atmospheric a pressure at a temperature between '30 and 80 C. The process may also be carried out under superatmospheric pressure, for example under a pressure from to 25 atmospheres, while employing temperatures above 100 C.

When the saponification mixture contains relatively large amounts of unsaponifiable constiuents, the' major portion thereof may be separated before the extraction by the addition of a small amount of the said alcohols, ethers, esters or ketones or of ethyl alcohol (as for example per cent calculated on the amount of saponification product) and allowing to settle, the residual saponification mixture then being freed in the said manner from the unsaponified or unsaponifiable constituents still present.

The extraction may advantageously be carried out in continuous manner, for example by treating the soap solution containing unsaponifiable constituents in counter-current with the said solvents- In this case it is preferable to employ towers containing fillers, such as l-taschig rings,

the liquid having the higher specific weight being cohols, as for example methyl or ethyl alcohol.

According to the said process it is possibleto remove from soap mixtures of the said kind the unsaponifiable or unsaponified constituents very rapidlyand to a far-reaching degree,as for, example down to about from 0.25 to 0.3 per cent tion. q

The solvents contained in the soap solutions -of the dry soap recovered from thesoap solution, without marked dilution of the soap solufreed from unsaponifiable constituents can be recovered in a very advantageous manner, while acidifying the soap solution with a mineral acid, as for example sulphuric acid, in an amount insuflicient for completely setting free the acids from the soaps and then, if desired, after withdrawing the-salt solution separated as lower layer, distilling off the solvents. In this manner the undesirable foaming of the solution to be distilled is avoided and a convenient separation of the water-insoluble solvents is effected.

The following examples will further illustrate the nature of this invention but the invention is not restricted to these examples. The parts are by weight, unless otherwise specified.-

Emample 1 100 parts of a crude soap mixture obtained by the oxidation of paraffin wax and neutralization and containing about 15 per cent of unsaponifh able constituents are dissolved in 250 parts of water and 30 parts of isobutyl alcohol, the solution then being extracted three times with 150 parts of a mixture of 9 parts by volume of trichlorethylene and 1 part by volume of isobutyl alcohol at C. From the soap solution thus purified by the addition of dilute sulphuric acid a crude fatty acid is obtained which upon examination according to Hiinig-Spitz shows only 0.3 per cent of unsaponifiable constituents.

Example 2 tion of the unsaponifiableconstituents separates. After separating the same, the soap solution is extracted while hot in an extraction apparatus for continuous operation in counter-current with a mixture of 9 parts by volume of benzine and 1 part by volume of isobutyl alcohol. The treated soap solution is freed from dissolved benzine and isobutyl alcohol by evaporation and acidified with dilute sulphuric acid. There is obtained a crude fatty acid which only contains 0.4 per cent of unsaponiflable constituents.

Example 3 100 parts of a product obtained by saponifying.

the acids from sperm oil with the calculated amount of a 20 per cent aqueous caustic soda solution, are diluted with 200 parts of water and extracted seven times, each time with 500 parts of a mixture of 5 parts by volume of benzene and 1 part by volume of normal propyl alcohol at 50 C. The soap dilution is decomposed with dilute sulphuric acid; the resulting fatty acid mixture has a content of only 0.1 per cent of unsaponifiable constituents.

Example 4 A product obtained by oxidizing paraflin wax with air at 120 C. while employing 0.15 per cent of potassium. permanganate as catalyst is saponified with caustic soda solution. The saponification product is subjected to an extraction with a mixture of 9 parts by volume of benzine and 1 part by volume of methyl-ethyl ketone betweenabout 40 and50 C., the unsaponiflable constituents being thereby removed.

To the soap solution obtained there is added half the amount of sulphuric acid of 50 per cent strength necessary for setting free all the fatty acids contained in the soap solution. The mixture is then evaporated in a distilling vessel until its volume is half of its original volume no foaming occurring during the distillation. The benzine and the methyl-ethyl ketone contained in the soap solution is recovered in a good yield and practically free from lowmolecular fatty acids. Tothe remaining mixture of fatty acids and soaps so much sulphuric acid is added as is necessary for completelysetting free the fatty acids from.

the soaps. The fatty acids are washed with water; they may be further purified by distillation and worked up to dry soaps.

What I claim is:

.1. The process .for recovering soaps of highmolecular aliphatic carboxylic acids from mixtures containing them besides unsaponiflable constituents, which comprises subjecting the said saponified mixtures to an extraction with a mixture of a solvent for fats and a solvent'selected from the class consisting of monohydric alcohols, ethers, esters and ketones containing from 3 to 6 carbon atoms in the molecule which in the presence of water is more soluble in the solvent for fats than in water.

2. The process for recovering soaps of highmolecular aliphatic carboxylic acids from a saponified oxidation product of high-molecular paraifin hydrocarbons which comprises subject ing the said saponiflcation products to an extraction with a mixture of a solvent for fats and a solvent selected from the class consisting of monohydric alcohols, ethers, esters and ketones containing from 3 to 6 carbon atoms in the molecule which in the presence of water is more soluble in the solvent for fats than in water.

3. The process for recovering soaps of highmolecular aliphatic carboxylic acids from a saponified oxidation product of high-molecular paraflin hydrocarbons which comprises subjecting the said saponification product to an extraction with a fat dissolving liquid hydrocarbon while adding a substance selected from. the class consisting of monohydric alcohols, ethers, esters and ketones containing from 3 to 6 carbon atoms in the molecule which in the presence of wateris more soluble in the solvent for fats than in water.

4. The process for recovering soaps of highmolecularaliphatic carboxylic acids from a saponified oxidation product of high-molecular paraffin hydrocarbons which comprises subjecting thesaid saponification productto an extraction with a mixture of benzine and a solvent selected from the class consisting of monohydric alcohols, ethers, esters and ketones containing from 3 to 6 carbon atoms in the molecule which in the presence of water is more soluble-in the solvent for fats than in water.

5. The process for recovering soaps of highmolecular aliphatic carboxylic acids from a saponified oxidation product of high-molecular parafiin hydrocarbons which comprises subjecting the said saponifi cation product to an extraction with a mixture of benzene with an alcohol containing from 3 to 6 carbon atoms which alcohol in the presence of water .is more soluble in the benzine than .in water.

, 6. The. process for: recovering soaps of highmolecular aliphatic .carboxylic acids. from a saponified oxidation product of high-molecular paraflin hydrocarbons which comprises subject- 75- in; the said saponification product to an extraction with a mixture of benzine and butyl alcohol.

7. The process for recovering soaps of high-.

molecular aliphatic carboxylic acids from mixtures containing them besides unsaponifiable constituents which comprises subjecting the said saponifled mixtures to an extraction in a continuous manner in counter-current with a mixture of a solvent for fats and asolvent selected from the class consisting of monohydric alcohols, ethers, esters and ketones containing from 3 to 6 carbon atoms in the molecule which in the presence of water is more soluble in the solvent for fats than in water.

8. The process. for recovering soaps of highmolecular aliphatic carboxylic acids from saponified mixtures containing them besides unsaponifiable constituents which comprises removing the major part of the unsaponifiable constituent as a layer from the soap solution then subjecting the soap solution to an extraction with a mixture of a solvent for fats and a solvent selected from the class consisting of monohydric alcohols, ethers, esters and ketones containing from 3 to 6 carbon atoms in the molecule which in the presence of water is more soluble in the solvent for fats than in water.

9. The process for recovering soaps of highmolecular aliphatic carboxylic acids from saponified mixtures containing them. besides unsaponifiable constituents which comprises subjecting the said mixtures to an extraction with a mixture of a solvent for fats and a solvent selected from the class consisting of monohydric alcohols, ethers, esters and ketones containing from 3 to 6 carbon atoms in the molecule which in the presence of water is more soluble in the solvent for fats than in water and setting free the fatty acids from the soap solution by acidifying it with a mineral acid.

WOLFGANG LEITHIE. 

